1. Field of the invention
The present invention relates to a false twisting device for producing crimped filamentary yarns, more particulary to a false twisting hollow spindle, provided with a turbin wheel, as a single body, and twisting pin laterally provided in the hollow space of the spindle. The hollow spindle is rotated by applying compressed air to the turbine wheel.
2. Description of the prior art
Generally, in a conventional false twisting device or apparatus, a twisting pin is laterally provided in center of a hollow of a false twisting spindle, so as to stabilize and/or balance the rotating motion of the hollow spindle. Due to the provision of the twisting pin, when the false twisting hollow spindle is rotated at a very high speed, undesirable yarn breakages frequently occur. That is, processing yarn fed into the hollow spindle is wound in one turn around the twisting pin and rotated, so that a portion of yarn entering the hollow of the spindle does not coincide with the rotating axis of the false twisting hollow spindle, but considerably deviates therefrom. Consequently, ballooning of the yarn caused by the centrifugal force of the spindle rotating at a very high speed, is accelerated and increased. Such generated yarn ballooning has little effect on yarn breakage while the hollow spindle is turning at a relatively slow speed, but, when the hollow spindle is driven at a very high speed, frequent yarn breakages do occur.
Referring to FIG. 1, which shows a basic type of the known false twisting device, yarn 2 supplied from a feed pin 1 is brought to a suitable tension by a pair of feed rollers 3, and a pair of delivery rollers 4. A yarn portion 2a of the yarn 2 entering a false twisting spindle 5, and disposed between the feed rollers 3 and the delivery rollers 4, is false twisted by the rotation of the false twisting spindle 5. After being thermally set the twists thereof are formed by a heater 6 sited between the feed rollers 3 and the false twisting spindle 5. Next, a yarn portion 2b of the yarn 2 which has passed through the false twisting spindle 5, and has been delivered from the delivery rollers 4, is wound on the yarn package 7. Ballooning is created in the yarn portion 2a entering into the false twisting spindle 5. However, ballooning is not created in the yarn portion 2b leaving from the false twisting spindle 5, because the yarn portion 2b is untwisted immediately after passing through the twisting pin provided in the hollow of the false twisting spindle 5. Further, the tension of the upstream yarn portion 2a on the twisting side becomes smaller than that of the downstream yarn portion 2b on the untwisted side by an amount corresponding to the contact resistance of the twisting pin 13.
FIG. 5 shows a cross-sectional view of a pressurized-air type false twisting spindle. A cylindrical hollow chamber 9 is formed at the central portion of the housing 8, and vertical hollow spindle 10 is supported by an upper and a lower bearing 11, 12 in concentric with the center line of the hollow chamber 9. A horizontal twisting pin 13 is provided in the hollow spindle 10 in such a position that the pin 13 traverses a vertical hollow 14 of the hollow spindle 10 in the diametric direction, and a turbine wheel 15 is secured to the outer peripheral surface of the hollow spindle 10 at the center portion. The bearings 11, 12, which support the hollow spindle 10, have grooves 16, 17 formed on the outer peripheral surface of the hollow spindle 10. A pair of upper 0-rings 18, 19 and a pair of lower 0-rings 20, 21 are respectively provided at both tip end portions of the outer peripheral surface of the hollow spindle 10. A horizontal upper air duct 22 and a lower air duct 23 facing toward the vertical hollows spindle 10 are formed in the grooves 16, 17, respectively. The upper and lower bearing 11, 12 are rigidly secured to the outer periphery of the hollow chamber 9 of the housing 8 by the upper and lower 0-rings 18, 19 and 20, 21, respectively. The hollow spindle 10 is engaged with the housing 8 at positions facing the upper and lower end portions of the hollow chamber 9, and screwed with an upper and a lower nuts 24, 25, respectively, so that dropping of the hollow spindle 10 from the housing 8 never occurs. In FIG. 5, 26 is an inlet aperture for the compressed air for rotating the hollow spindle 10, 27 is an outlet aperture for exhausting air from the hollow spindle 10, while 28 indicates an inlet aperture of compressed air for the bearings 11, 12, and 29, 30 are branch tubes of the inlet aperture 28.
FIG. 2 shows a cross-sectional view of a conventional hollow spindle 10. In FIG. 2, a rotational axis 31 of the hollow spindle 10 and a center point 33 of the smallest diameter portion 32 of the twisting pin 13 coincide with each other. As stated before, the yarn portion 2b leaving the hollow spindle 10 has a greater tension than that of the yarn portion 2a entering the hollow, spindle 10, and therefore, the position of this yarn portion 2b coincides with the smallest diameter portion 32 of the twisting pin 13. On the other hand, the position of the yarn portion 2a on the false twisting side is displaced both in the parallel and vertical directions with reference to the axis of the twisting pin 13 by amounts equal to a diameter 2 of the yarn portion 2a and equal to 1 which is the sum of the radius of the smallest portion 32 of the twisting pin 13 and the radius of the yarn portion 2a, respectively. As a result, ballooning of the yarn portion 2a on the false twisting side is accelerated and/or magnified by rotation of the hollow spindle 10, so that various kinds of trouble arise. These are detailed as follows:
That is,
1. when the compressed air type false twisting spindle 10, of light weight (shown in FIG. 5), is driven at a very high speed, the spindle 10 vibrates and the bearing 11, 12 in the housing 8 contact the vibrating spindle 10, so that rapid wear of the bearings 11, 12 and/or the spindle 10 takes place.
2. In any type of false twisting spindle, whether of the compressed air driven type or frictional force driven type, twists of the ballooning yarn accumulate at a position adjacent to the twisting pin 13, so that propagation of the twists is prevented and, further, since the yarn which passes through the twisting pin 13 is in an insufficiently untwisted condition, the processed yarn produces continuously swelled untwisted portions;
3. The ballooned yarn contacts the inside wall of the hollow 14 of the spindle 10, so that the yarn is frequently broken and the yarn strength lowered.
Of the above-mentioned problems, the most difficult is the phenomenon of yarn breakages causes, and unless such problems are completely eliminated, it is impossible to carry out in practice, a false twisting operation by a false twisting spindle driven at speeds higher than 400,000 r.p.m.